With regarding to general duplex modes adopted in a cellular system, a Time Division Duplex (TDD) mode refers to transmission of uplink and downlink signals in the uplink and downlink with the same operating frequency band in different periods of time, where there is a Guard Period (GP) between the uplink and downlink; and a Frequency Division Duplex (FDD) mode refers to possible transmission of uplink and downlink signals in the uplink and downlink with different operating frequency bands at the same time over different frequency carriers, where there is a Guard Band (GB) between the uplink and downlink.
A frame structure of a Long Term Evolution (LTE) TDD system is somewhat complicated, and as illustrated in FIG. 1A, a radio frame with a length of 10 ms includes 10 sub-frames in total including special sub-frame(s) and normal sub-frames, and each sub-frame is of 1 ms. The special sub-frame includes three time slots, a Downlink Pilot Time Slot (DwPTS) for transmitting a Primary Synchronized Signal (PSS), a Physical Downlink Control Channel (PDCCH), a Physical HARQ Indication Channel (PHICH), a Physical Control Format Indication Channel (PCFICH), a Physical Downlink Shared Channel (PDCCH), etc.; a GP for a guard period between the downlink and uplink; and an Uplink Pilot Time Slot (UpPTS) for transmitting a Sounding Reference Signal (SRS), a Physical Random Access Channel (PRACH), etc. The normal sub-frames include uplink sub-frames and downlink sub-frames for transmitting uplink/downlink control signaling, service data, etc. Particularly in one radio frame, two special sub-frames may be configured in sub-frames 1 and 6 respectively or one special sub-frame may be configured in the sub-frame 1. Sub-frame 0 and sub-frame 5, and the DwPTS in the special sub-frame(s) are always used for downlink transmission, Sub-frame 2 and the UpPTS in the special sub-frame(s) are always used for uplink transmission, and the remaining sub-frames can be configured as needed for uplink transmission or downlink transmission.
In a TDD system, the same frequency resource is used for uplink and downlink transmission, and uplink and downlink signals are transmitted in different time slots. In a common TDD system including 3G Time Division Synchronized Code Division Multiple Access (TD-SCDMA) system and a 4G TD-LTE system, uplink and downlink sub-frames are allocated statically or semi-statically, and a common practice is to determine and maintain a proportional allocation of uplink and downlink sub-frames dependent upon a cell type and a rough service proportion in the course of planning a network. This is a simple and effective practice in a context with large coverage of a macro cell. Along with the development of technologies, an increasing number of low-power base stations including home NodeBs and so on in a pico cell have been deployed for provision of small local coverage, and there are a small number of users with a significantly varying service demand in this kind of cell, thus there exists a scenario with a dynamically varying demand for an uplink and downlink service proportion in the cell.
In order to accommodate such a dynamically varying demand for a service proportion, some researchers come to consider optimization of the TDD system by introducing a more dynamic uplink and downlink configuration solution with the aim of accommodating a varying service proportion and improving the efficiency of the system. For example in a TDD network, a macro cell is configured with a relatively symmetric uplink and downlink proportion (DL:UL=3:2), and a part of femto cells are configured with a downlink-dominant proportion (DL:UL=4:1) in view of a predominating user demand for download, while another part of femto cells are configured with a uplink-dominant proportion (DL:UL=2:3) in view of a predominating user demand for upload.
If adjacent cells are configured with different uplink and downlink proportions, then there may be interference across time slots. In FIG. 1B, a macro cell transmits a downlink signal in a time slot in which a femto cell receives an uplink signal, then between the two cells:
Inter-NodeB interference may arise in that direct reception of the downlink signal of a macro NodeB by a femto NodeB will influence seriously the quality of the uplink signal of a Local UE (L-UE) received by the femto NodeB.
The foregoing interference may influence seriously the performance of the entire network, but there is no solution in the prior art to such an interference problem.